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Groundwater Depletion in Chicago’s Southwestern Suburbs

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Sandstone aquifers are a major water resource in Northeast Illinois, but these aquifers have experienced declining water levels since the first well was drilled into them in 1863. In modern times, sandstone water supplies in the southwest suburbs are at the highest risk, where water levels have reached historic lows, exceeding 1,100 feet of drawdown when wells are pumping. That’s equivalent to water levels having fallen by 88 floors of Willis Tower, and by 2040, the regional trend suggests that drawdown will have reached the top floor!

New analysis by the Illinois State Water Survey, using a combination of data and modeling, suggests up to 50% of the sandstone water use in northeast Illinois is unsustainable, further emphasizing this water resource will be unable to accommodate increasing water demands in the region. Most areas should reduce their water use to avoid potential problems, else widespread water supply issues will propagate throughout portions of Will, Kendall, and Kane Counties. Model simulations have suggested additional development near the highest risk areas may quickly deplete the aquifer to the point that it is unusable for nearby wells, resulting in local impacts that may happen much earlier than what the regional trend would suggest.

Understanding the depletion of the deep groundwater in northeastern Illinois is critically important to water supply planners, and will require decisions be made on both local and regional scales. Fortunately, there are alternate sources of water available, including Lake Michigan and the Fox and Kankakee Rivers, but planning should start now to avoid a water crisis.

A 2-page summary of the depletion of the sandstone aquifers can be found here. Visit the Water Survey’s water supply page for lots of information and resources.